EVALUATION OF PROGNOSTIC FACTORS FOR DOGS WITH SYNOVIAL SARCOMA - 36 CASES (1986-1991)

Medical records of 36 dogs with synovial sarcoma confirmed by microsco pic examination of H&E-stained sections of tissue were selected for re trospective analysis from dogs admitted between 1986 and 1991 to parti cipating institutions of the Veterinary Cooperative Oncology Group. Me tastasis was evident at the time of diagnosis in 8 (22%) dogs, and 15 (41%) dogs ultimately developed metastatic tumors. Median survival tim e for all dogs, as determined by life-table analysis, was 17 months. F or dogs that were subsequently treated and became tumor free, the medi an disease-free interval was 30 months. Nine dogs had previously had l ocalized excision attempted, but all had recurrence of the tumor local ly (median, 4.5 months). Of 29 dogs that underwent amputation, includi ng the 9 with localized recurrence, 2 had tumor recurrence on the ampu tation stump. Most dogs had survival time and disease-free interval of > 36 months after amputation. Four dogs that had received chemotherap y for tumors of advanced clinical stages did not respond to treatment. One dog that had received locally applied radiotherapy after localize d excision did not have evidence of tumor recurrence 2 years after rad iotherapy. Clinical stage, histologic grade, and a positive result for tests that used cytoheratin immunohistochemical staining significantl y (P < 0.05) influenced survival time and disease-free interval. Analy sis of data for the study reported here suggested that histologic crit eria can be an excellent predictor of dogs that are likely to have tum or recurrence after amputation and that would most likely benefit from aggressive treatment with adjuvants.